This invention relates, in general, to electronic components, and more particularly to molding material used in optical components used for transmitting and receiving an optical data signal.
Many opto-electronic applications involve passing an optical signal from a signal generator to a signal detector. For example, an opto-isolator uses a light emitting diode (LED) to transmit data from one circuit to a light detector in another circuit. The use of the LED allows the two circuits to be electrically and physically isolated from each other, yet remain in communication with each other. Other examples include passing an optical signal from a light emitter to a light detector by directing an optical signal through a wave guide or optical fiber, or off a reflective dome/lens.
In all of these applications, the assembly of the optical device must be compatible with each of the individual components that make up an optical device (e.g., leadframe, leads, semiconductor devices, bonding wires, and the package). In other words, the process that is used to assemble an optical component must be tailored so as to minimize the amount of thermo-mechanical stress that is placed on the individual components and the amount of similar stress that occurs within the optical component while the component is in use by a customer.
Of the existing mold compounds that are used in the assembling of optical components, most suffer from one of three limitations. First, they often have a coefficient of thermal expansion (CTE) that causes a device to be damaged as the device undergoes wide temperature variations. Secondly, most mold compounds have a glass transition temperature (Tg) that causes the compound to become soft and rubbery under conventional assembly process conditions. Finally, existing mold compounds have an index of refraction value that is incompatible with the requirements of many optical electronic applications.
Accordingly, a need exists to provide a mold compound that is both compatible with existing assembly processing requirements and with the optical requirements of optical electronic devices.